The effect of ultrasonic pretreatment and sample preparation on the extraction yield of antioxidant compounds and activity of black currant fruits.

The aim of the study was to evaluate the efficiency of an ultrasonic pretreatment at different amplitudes and extraction times, on the content of antioxidant compounds (phenolics, anthocyanins, ascorbic acid) and total antioxidant capacity of black currant fruits. Additionally, the influence of sample preparation (frozen storage/drying) was evaluated. Extraction was performed in 60% ethanol with 0.15% HCl at a solvent-to-sample ratio of 15/1. Our results show that the ultrasonic pretreatment proved particularly useful for the recovery of high amounts of total anthocyanins in freeze-dried samples, ascorbic acid in frozen and oven air-dried samples, and total antioxidant capacity in freeze-dried and oven air-dried samples. The total phenolics content was not significantly influenced by the ultrasonic pretreatment. Freeze-drying increased the content of targeted compounds, to a very high significant level (p < 0.001) for anthocyanins and ascorbic acid. Oven air-drying at 45 °C drastically decreased the ascorbic acid content. Ultrasonication enhanced the extraction yield of black currant valuable compounds in strong relation to the operating conditions.